This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-263787, filed Sept. 17, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a distance-measuring apparatus and a distance-measuring method for a camera.
The distance-measuring apparatus for a camera uses either distance-measuring methods of an active type or those of a passive type. Among these, the active-type method performs the distance-measuring by projecting signal light from a camera and using its reflected signal light, whereas the passive-type method carries out focusing by using image signals in the picture image plane.
Since in the passive-type distance-measuring apparatus a dynamic measure of a distance-measuring sensor is limited, it is difficult to carry out image detection of all subjects so as to have a proper luminance level in scenes where various subjects may have a variety of luminances in the image plane. Then, to solve this problem, the U.S. Pat. No. 5,721,977 (corresponding to Japanese Published Unexamined Patent Application No. 10-161010) discloses a technology whereby pixels whose integration has been completed are selected on the basis of the photometric value, the photographing mode, and the focal length.
In addition, it is extremely difficult to select a main subject (a photographer""s intended subject) among all photographing subjects and if this selection doesn""t work well, there may be a case where an image of the subject to be measured becomes too dark to perform the distance-measuring and miscellaneous images having no necessity of being measured. In such cases, neither the correct distance-measuring nor correct focusing can be performed.
On the contrary, in the camera capable of focusing only a specific area in the image plane, the freedom of composition is restricted. To cope with this problem, the camera capable of measuring multiple points in the image plane has been devised. However, multiple-point distance-measuring like this needs a contrivance that considers the above-mentioned problem (selection of the proper distance-measuring point) even more extensively.
The above-mentioned U.S. Pat. No. 5,721,977 discloses the improvement to a comparatively narrow area and leaves a subject in lengthwise composition and a subject located at one of the corners of the image plane out of consideration. Thus, the conventional technology cannot carry out correct focusing that corresponds to various photographing scenes by making possible distance-measuring on several points in a wide area of the image plane.
Therefore it is the object of the present invention to provide the distance-measuring apparatus for a camera capable of measuring several points in a wide area of the image plane and controlling image signals so as to have a proper level within the dynamic measure of image signal detecting means while giving the freedom of setting distance-measuring positions according to the subject position with an intention of making possible correct focusing that corresponds to various photographing scenes.
To achieve the above-mentioned object, a first aspect of the present invention discloses a distance-measuring apparatus for a camera comprising: an area sensor for light-receiving a picture image in the image plane; an integration circuit for integrating output signals of this area sensor; an integration control circuit for controlling an operation of starting the integration and an operation of stopping the integration of the above-mentioned integration circuit based on output signals that correspond to a specific block of the above-mentioned area sensor; and a switching circuit for switching the above-mentioned specific block according to the using state of the camera.
Moreover, a second aspect of the present invention discloses a distance-measuring apparatus for a camera comprising of: a sensor array; first integration means to measure a subject image distribution in the image plane based on outputs of this sensor array; determining means for determining a specific area in the above-mentioned sensor array for making integration judgment at the time of the distance-measuring in accordance with a measurement result of the above-mentioned subject image distribution by this first integrating means; and second integrating means for controlling the integration of the above-mentioned sensor array based on signals from the above-mentioned specific area determined by the above-mentioned determining means in order to measure the image signal at the time of the above-mentioned distance-measuring.
Furthermore, a third aspect of the present invention discloses a method for performing the distance-measuring for a camera comprising: a first integration step of integrating image signals in the above-mentioned image plane to specify a main subject in the image plane; a second integration step of integrating image signals of the above-mentioned main subject; and a calculation step of calculating the distance to the above-mentioned main subject by using a result of the above-mentioned second integration step, wherein the above-mentioned first integration step and the above-mentioned second integration step have respective sets of pixels which form different shapes and wherewith the integration judgment is made. moreover, a fourth aspect of the present invention discloses a distance-measuring apparatus for obtaining the distance to the subject comprising of: an area sensor; detecting means for detecting a subject image using outputs of this area sensor; and switching means for setting integration judgment areas which are formed by selecting and combining a plurality of pixels in the above-mentioned area sensor and controlling the above-mentioned judgment area so as to take a plurality of shapes in order to control the above-mentioned subject image to be within a proper integration measure.
Moreover, a fifth aspect of the present invention discloses a distance-measuring apparatus for a camera comprising: an area sensor that can use a plurality of areas in a two-dimensional light-receiving area as monitor areas for integration control; emission means for projecting light toward the subject; monitor selecting means for making the above-mentioned emission means operate, receiving reflected light from the above-mentioned subject with the area sensor at this moment, and selecting the above-mentioned monitor area based on outputs thereof; and controlling means for conducting the integration control of the output signals of the above-mentioned area sensor based on the outputs of the monitor area selected by the above-mentioned monitor selecting means.
Moreover, a sixth aspect of the present invention discloses a distance-measuring apparatus of a camera comprising: (a) a plurality of area sensors of a main system and a sub system; setting means for setting monitor area(s) to be used for controlling an integral time of the above-mentioned area sensor of the main system based on image information of the above-mentioned area sensor of the sub system and photographing information inputted according to the photographer""s intention; integration controlling means for controlling an integral time of the above-mentioned area sensor of the main system based on outputs of the above-mentioned monitor area; and arithmetic means for obtaining the distance to the subject based on outputs of the above-mentioned area sensor of the main system.
Moreover, a seventh aspect of the present invention discloses a camera comprising: an area sensor composed of a plurality of pixels for light-receiving an optical image in the photographing image plane; a selection circuit for determining a specific area in the above-mentioned area sensor; and an integration control circuit for controlling an integral time of output signals from the above-mentioned area sensor based on pixel outputs of the above-mentioned specific area selected by this selection circuit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.